In recent years, ceramic electronic components have been extensively used, and ceramic multi-layer substrates with built-in coil conductors have been widely used.
For example, Japanese Patent No. 4703459 proposes a built-in coil substrate including: a pair of insulating bases; a ferrite magnetic layer provided between the pair of insulating bases; a planar spiral coil formed in the ferrite magnetic layer; a highly magnetic body provided in the central area of the planar spiral coil, which has a higher magnetic permeability than the ferrite magnetic layer; and a non-magnetic body provided between the planar spiral coil and the highly magnetic body, which has a lower magnetic permeability than the ferrite magnetic layer.
Japanese Patent No. 4703459 states that Cu, Ag, Au, Pt, Ag—Pd alloys, Ag—Pt alloys, etc. can be used as the metal materials for use in the coil conductors.
In addition, International Publication No. 2007/145189 proposes a laminate-type ceramic electronic component provided with a ceramic laminate body which has a laminate structure including a ceramic base material layer composed almost entirely of a polycrystalline phase, and a ceramic auxiliary layer placed on at least one principal surface of the ceramic base material layer and composed almost entirely of a polycrystalline phase, which is obtained by co-firing with the ceramic base material layer; and a conductor pattern provided inside and/or outside the ceramic laminate body.
In International Publication No. 2007/145189, Ag is used as the conductor pattern.